Clearly, miniaturization is a main object of all electronic packaging developers and manufacturers. Accordingly, various electronic packages have been introduced within the past few (e.g., ten) years which accomplish this objective, examples being defined and illustrated in detail in the following U.S. Patent Numbers:                U.S. Pat. No. 4,937,707—McBride et al        U.S. Pat. No. 5,057,969—Ameen et al        U.S. Pat. No. 5,159,535—Desai et al        U.S. Pat. No. 5,435,732—Angulas et al        U.S. Pat. No. 5,519,936—Andros et al        
Typically, such packages utilize extremely small conductive members such as spherically-shaped solder balls as the connecting medium. Such solder balls may possess a diameter of only about 0.025 inch to about 0.035 inch, and in the final product for incorporation within a larger electronic structure (e.g., a microprocessor), are typically arranged in compact, highly dense arrays (e.g., those with the balls positioned apart on only 0.050 inch centers). The electrical circuitry for such packages is also highly dense, and may possess line widths as small as about 0.002 inch, with 0.002 spacings between lines. Even smaller elements are presently being contemplated for future products.
An excellent example of one such product is the HyperBGA® electronic package sold by the assignee of this invention. (HyperBGA is a registered trademark of the assignee, Endicott Interconnect Technologies, Inc.). This structure includes a laminate substrate with exceptional thermal compensating properties capable of effectively coupling at least one semiconductor chip thereon to an underlying substrate (e.g., printed circuit board), using such solder balls as mentioned above for both connections.
It is readily understood that testing of such substrates is a critical and necessary step during the manufacture thereof, in order to prevent subsequent failure when the package is utilized in a larger (and very expensive) assembly such as a microprocessor or the like. It is also understood that such testing can be a difficult, complex and time-consuming operation.
Examples of various means for testing electronic structures are illustrated in the following U.S. Letters Patents. In U.S. Pat. No. 4,105,970 (Katz), a test pin with a jagged edge is utilized, while in U.S. Pat. No. 4,686,464 (Elsasser), buckling beam connectors are used. A printed circuit board tester using a plurality of apparently spring-loaded pin contacts is described in U.S. Pat. No. 4,851,765 (Driller et al) and an electrical circuit test probe, also spring-loaded, is described in U.S. Pat. No. 4,885,533 (Coe). U.S. Pat. No. 5,032,787 (Johnston) describes an elongated test probe with a spring-loaded plunger which is rotated during movement to make contact with the desired object being tested, while U.S. Pat. No. 5,204,615 (Richards et al) describes a module claimed to be able to test “linear high density” test site arrays. U.S. Pat. No. 5,391,995 (Johnston) describes a spring-biased test probe having an end configured to make frictional pressure contact with the test site (e.g., a board). And, in U.S. Pat. Nos. 5,804,984 and 6,051,982, there are defined two test apparatus also using spring-biased contacts for testing such electronic packages as exemplified above (e.g., the HyperBGA® package). Both patents are co-authored by the inventor of the instant invention. In IBM Technical Disclosure Bulletin (TDB) Vol. 25, No. 1, B (April, 1983), there is defined a spring-loaded probe with a rotational wiping feature, the probe having a jagged tip portion. In IBM TDB vol. 37, no. 02B (February, 1994), another example of the aforementioned buckling beam connectors is defined.
When simultaneously testing pluralities of conductive members such as the above-described extremely small solder balls arranged in a highly dense array, it is quickly understood that precisioned alignment and proper pressure application of each test contact probe member are critical. Clearly, these contacts must maintain a spaced relationship from one another (or shorting can occur during test), and must also allow ease of movement of the individual probes toward and away from the object being tested. Equally important, these cannot exert excessive pressure onto the solder balls and/or the pads on which these are positioned because doing so could harm the underlying pad or dielectric layer supporting same. It is not believed that the test apparatus described in the above patents and published documents (TDBs) can provide such connection and movement in an effective and cost-efficient manner capable of meeting many of today's demanding production schedules.
It is believed, therefore, that a test apparatus capable of effectively testing highly dense arrays of conductive members such as small diameter solder balls in a precise yet expedient manner utilizing the optimum forces necessary on the balls such as taught herein would constitute a significant advancement in the art.